1. Field of the Invention
The present invention relates to power sources for portable electronic devices and more specifically relates to a photovoltaic power source for operating and charging a portable electronic device.
2. Discussion of Related Art
Popularity of portable electronic devices for computing and communications is growing at a rapid pace. Such portable devices include, for example, cellular telephones, portable telephones, personal digital assistants (PDAs), portable computers (laptops and notebooks), etc. Batteries typically power such portable electronic devices. To reduce costs in such devices, the batteries are typically rechargeable to thereby reduce costs incurred by the user for frequent replacement of nonrechargeable batteries.
A common problem for all such battery-powered portable electronic devices is the need to recharge the batteries of the device. In general, as presently practiced in the art, recharging the batteries of such a portable electronic device entails plugging the device into a nearby power source via a cable or cord. For example, a cellular phone may be plugged into an associated AC adapter to recharge its batteries from power supplied by a standard wall outlet. Similarly, automobile adapters allow a cellular telephone to recharge from an automobile""s power source.
All presently known in techniques and apparatus for recharge in the batteries of such a portable electronic device involve plugging the electronic device into an appropriate power source and permitting the device to be recharged. Although presently known charging systems permit the device to be used in during the recharge, presently known charging systems involve a cord or cable connecting the portable electronic device to a suitable power source. Portability of the electronic device is thereby diminished due to the constraints of the attached cable or cord.
In view of the above discussion it is evident that a need exists for improved power source and charging designs for portable electronic devices whereby true portability of the device is maintained while charging.
The present invention solves the above and other problems, thereby advancing the state of the useful arts, by providing structure and methods for utilizing photovoltaic cells and associated switching and charging circuits to provide charging for batteries in portable electronic devices. Use of a photovoltaic cell for providing power and charging of batteries in a portable electronic device retains full portability of the device while charging the batteries.
The charging system of the present invention may be beneficially utilized in conjunction with most portable electronic devices including in particular, cellular phones, portable phones, PDAS, and portable computers. In one preferred exemplary embodiment, the photovoltaic cell is mounted to an external surface of a cell phone such that it is normally exposed when the cell phone is inserted in a carrying cradle or case. When exposed to appropriate frequencies of light (e.g., sunlight) the photovoltaic cells and associated charging circuits provide a constant source of charging power for the batteries of the cellular phone. Similar designs in other preferred embodiments permit similar charging for batteries associated with portable phones, PDAs, or portable computers.
A state machine circuit of the present invention provides for automatic switching of the power generated by the photovoltaic cells into a charging mode for recharge in the batteries as well as a primary power mode for use as the primary power source in operating the portable electronic device.
A number of implementation design choices are possible for implementing features of the present invention. In a first preferred embodiment, photovoltaic cells are connected to the state machine and associated current control circuits fabricated directly with the photovoltaic cell array as an integrated component thereof. In a second preferred embodiment, the photovoltaic cells and the state machine and associated current control circuits are fabricated in separate components thereby permitting additional modularity in the selection of photovoltaic cells for particular applications. In yet another preferred embodiment, the charging state machine and associated current control circuits are integrated directly with custom devices and circuits within the portable electronic device. Such a solution may help reduce total component cost for low-end electronic devices. The various embodiments each provide particular benefits with respect to particular attributes of the circuits including modularity, flexibility of circuit design selections, integration and costs.
These and other features, aspects and benefits of the present invention will be readily apparent to those skilled in the art through a more careful reading of the following description and associated drawings as follows.